Flame spreader with stress relief for a burner

ABSTRACT

A burner spreader which is subjected to thermal stresses during cycling of a burner has a flame spreading rim supported by struts connected to the burner. Stress relief portions connect the ends of the struts to the flame spreading rim.

United States Patent 1 Katchka 51 Nov. 5, 1974 1 FLAME SPREADER WITH STRESS RELIEF FOR A BURNER [75] Inventor: Jay R. Katchka, Cypress, Calif.

[73] Assignee: Robertshaw Controls Company,

Richmond, Va.

[22] Filed: Sept. 28, 1973 [21] Appl. N0.: 401,785

[52] US. Cl 431/285, 431/80, 431/171, 431/347 [51] Int. Cl. F23g 9/00 [58] Field of Search 431/347, 285, 92, 80, 171; 236/15 A [56] References Cited UNITED STATES PATENTS Johnson 431/347 R 3,182,712 5/1965 Zink et al. 431/347 X 3,754,853 8/1973 Brauzksiek et a1. 431/285 3,762,639 10/1973 Katchka et a1 431/285 X Primary Examiner-Edward G. Favors Attorney, Agent, or FirmAnthony A. OBrien ABSTRACT A burner spreader which is subjected to thermal stresses during cycling of a burner has a flame spreading rim supported by struts connected to the burner. Stress relief portions connect the ends of the struts to the flame spreading rim.

8 Claims, 5 Drawing Figures BACKGROUND OF THE INVENTION 1. Field of the Invention:

The invention relates to gaseous fuel burners and in particular to burners operable at both high and low rates.

2. Description of the Prior Art:

Prior art plural rate burners employ an annular SUMMARY OF THE INVENTION The invention is summarized in that a flame spreader for a burner includes mounting means including a plurality of radially extending supporting struts, an annular flame spreader portion, and a plurality of stress relief portions joining the plurality of struts to the annular flame spreader portion.

An object of the invention is to eliminate cracking and fracturing at the junction of struts supporting a flame spreader.

Another object is to construct a flame spreader having supporting struts attached in a manner to allow expansion and contraction of the flame spreader during cyclic operation of a burner.

It is also an object of'the invention to construct a plural rate burner with an improved and longer lasting flame spreader.

Other features of the invention include the provision of flexible elongated partially severed arcuate portions of an annular flame spreader connecting the annular flame spreader to supporting struts for distributing thermal stress throughout substantial lengths of the partially severed arcuate portions; and the provision of a stress relief strip isolated by a stamped boundary, the strip having a width less than the width of a supporting strut and having a length extending from the strut to a flame spreader greater than the width of the strut.

Other objects, features and advantages of the invention will become apparent from the following descrip? tion of the preferred embodiment taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram of a burner apparatus in accordance with the invention.

FIG. 2 is a cross section view of a portion of the burner apparatus shown in FIG. I illustrating a low rate of operation.

FIG. 3 is a view similar to FIG. 2 but only partially in cross section and illustrating a high rate of operation.

FIG. 4 is a plan view of a flame spreader of the burner apparatus of FIG. 1.

2 FIG. 5 is a cross section view of the flame spreader shown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT As illustrated in FIG. 1 the present invention is embodied in a fuel burner apparatus for an appliance, such as a hot water heater indicated generally at 10. The burner apparatus includes a burner indicated generally at 12connected by a conduit 14 and a line 16 to a fuel control device 18 which is connected to a gaseous fuel source (not shown). The control device 18 includes thermostat facilities (not shown) for selectively applying a low pressure gas to conduit 14 for standby or low rate operation of the burner 12, and applying a high pressure gas to conduit 14 for high rate operation of the burner 12. Also the control device 18 includes safety valve facilities (not shown) controlled by conditions in line 16 to terminate gas flow to the conduit 14 in the event there is an absence of flame in the burner 12. A suitable control device is disclosed in US. Pat. application Ser. No. 98,246 by Jay R. Katchka and Henry C. Braucksiek filed on Dec. 15, 1970, now US. Pat. No. 3,762,639.

The burner 12, shown in FIG. 2, includes a burner member indicated generally at 22 formed from an outer tubular section 24 and an inner tubular section 26 which are coaxial about a vertical axis and joined at upper and lower ends to form an annular chamber 28. An inlet or nipple 30 is secured in an opening 32 formed in the outer tubular section 24 and communicates with the conduit 14. A plurality of outward-facing and circumferentially-spaced ports 34 are formed in the outer tubular section 24 while an inwardly and upwardly directed burner port 36 is formed in a deformed portion 38 of the inner tubular section 26.

A flame sensing element 40 connected to the line 16 is mounted within a tubular spring clip support 42 mounted on a bottom plate 44 secured to the lower end of the burner member 22. The flame sensing element 40 extends along the vertical axis above the upper end of the burner member 22. Openings 46 in the plate 44 are of a size to allow sufficient air flow to sustain combustion of the fuel emitted from burner port 36. The flame sensing element 40 is any suitable device, such as a thermocouple for generating conditions, such as electric currents or voltages in line 16 to operate the safety valve facilities.

A flame spreader and shield support indicated gener ally at 48 has a collar 50 mounted on the upper end of the burner member 22. A frustro-conical shield 52 is mounted by tabs 54 to an annular flame spreader portion or rim 56 of the flame spreader 48. The shield 52 has legs 58 supporting a spaced top 60 to provide ventilation for upward extending flames from the burner member 22.

As shown in FIGS. 4 and 5, the flame spreader 48 has struts 62 joining the collar 50 to the rim 56 with flame protecting tabs 63 extending downward from the struts 62. The collar 50, the struts 62 and the rim 56 form openings 64 for passing upward extending flames from the ports 34. The rim 56 has an upward extending flange 66 and an annular rib 68. Stress relief portions 70 of the rim 56 are isolated or partially severed by lanced or cut portions 72 from the remaining part of the rim 56. Each of the portions 70 is an arcuate strip which extends transversely in opposing directions from a junction with a respective strut 62. The widths of the strips 70 are less than the widths of the struts 62 and the lengths of the strips 70 extending from the struts to the remaining portion of the rim 56 is greater than the widths of the struts 62 to impart sufficient flexibility to the junction of the struts 62 and the rim 56 to prevent cracking or fracture of the junction. The cut portions 72 are shown as stamped sections which are stamped cleanly to form completely severed boundaries 73 between the cut portions 72 and the strips 70.

ln operation of the burner system shown in FIG. 1, the control device 18 in response to the thermostat facilities selectively supplies a low pressure gaseous fuel to the conduit 14 and the annular chamber 28 or a high pressure gaseous fuel to the conduit 14 and the annular chamber 28. At the standby or low rate of operation, illustrated in FIG. 2, low pressure fuel being emitted from the burner ports 34 sustains a flame which follows the outside wall of the burner member 22 upward through the openings 64 between the struts 62 and converges inward against the flame sensing element 40 above the upper end of the burner member 22. The shield 52 and tabs 63 protect the upward extending flame from being extinguished by air currents or drafts. At the high rate of operation, illustrated in FIG. 3, high pressure fuel projects from the ports 34 to sustain outward extending flames from beneath the flame spreading rim 56; and fuel from the port 36 sustains an inwardly and upwardly directed flame impinging upon the flame sensing element 40. At both the low and high rates of operation the flame sensing element 40 through line 16 maintains the safety valve facilities in the control device 18 open to allow operation of the burner 12. If the absence of a flame in the burner 12 is sensed by the flame sensing element 40, the safety valve facilities are closed to terminate flow of fuel to conduit 14 to prevent the hazardous release of fuel.

During the cyclic operation of the burner apparatus, the struts 62 are subjected to heating by the upward extending low rate flames, and the flame spreading rim 56 is subjected to heating by the outward extending high rate flames. ln addition the struts 62 support the weight of the shield 52. The stress relief portions 70 joining the struts 62 to the rim 56 prevent cracking and fracture at the junction of the struts 62 to the rim 56 due to stress including thermal stress from alternate expansion and contraction of the rim 56 and struts 62; thus resulting in a more reliable and longer lasting burner apparatus. The stress reliefs portions '70 also prevent cracking where the struts 62 join the collar 50.

Having the stress relief portions 70 formed from partially severed arcuate strips of the rim 56 is particularly advantageous from both economical and technical view points. The severed boundary '73 can be formed during manufacturing steps utilized in forming the flame spreader 48 without the necessity of adding any additional steps. The extension of the arcuate strips 70 transversely from the struts 62, the width of the strips 70 being less than the width of the struts 62, and the length of the strips 70 extending from the struts 62' ing wall increases the rate of thermal change adding to the degree of thermal stress. The stress relief portions 70 substantially reduce fracture of plural rate burner apparatus in water heaters.

Since many variations, modifications and changes in detail can be made to the present embodiment it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interrupted as illustrative and not in a limiting sense.

What is claimed is:

l. A flame spreader for a burner comprising mounting means including a plurality of radially extending supporting struts,

an annular flame spreader portion, and

a stress relief portion joining one of the plurality of struts to the annular flame spreader portion.

2. A flame spreader as claimed in claim 1 wherein the stress relief portion extends transversely from the one strut to the annular flame spreader portion.

3. A flame spreader as claimed in claim 1 wherein the stress relief portion includes a strip extending transversely in opposing directions from the one strut, said strip having a width less than the width of the one strut and having a length extending from the one strut to the spreader portion greater than the width of the one strut.

4. A burner apparatus operable at a high rate and a low rate comprising a round burner member disposed about a vertical axis and having an inlet and a plurality of outward directed ports circumferentially spaced in the burner member to produce an outward extending flame at the high rate and an upward extending flame at the low rate; and

a flame spreader having a plurality of struts extending radially from the burner member with openings between the struts for allowing passage of flame, an annular flame spreader portion for spreading the outward extending flame, and a plurality of stress relief portions joining the plurality of struts to the annular flame spreader portion.

5. A burner apparatus as claimed in claim 4 which includes a flame shield mounted on the annular flame spreader portion and extending around the path of the upward extending flame.

6. A burner apparatus as claimed in claim 4 wherein each of the plurality of stress relief portions includes a strip extending transversely in opposing directions from a respective strut and having a length extending from the respective strut to the spreader portion greater than the width of the respective strut. 7. A burner apparatus operable at a high rate and a low rate comprising an annular burner member disposed about a vertical 6 axis and having an inlet and a plurality of outward directed ports circumferentially spaced in the burner member; control means for selectively applying gaseous fuel at a low pressure to the inlet of the burner member to produce an upward extending flame from the ports, and applying gaseous fuel at a high pressure to the inlet of the burner member to produce an outward projecting flame from the ports;

a flame spreader having a flame spreading rim, a collar mounted on the burner member above the ports, and a plurality of struts extending radially from the collar to the flame spreading rim;

said struts, collar and rim forming openings for passing the upward extending flame;

a flame sensing element disposed along the axis of the burner member and extending above the burner member in the path of the upward extending flame;

safety valve means responsive to the flame sensing element for controlling fuel flow to the burner member;

means responsive to the application of high pressure fuel to the burner member for directing a flame at lationship relative to the rim. 

1. A flame spreader for a burner comprising mounting means including a plurality of radially extending supporting struts, an annular flame spreader portion, and a stress relief portion joining one of the plurality of struts to the annular flame spreader portion.
 2. A flame spreader as claimed in claim 1 wherein the stress relief portion extends transversely from the one strut to the annular flame spreader portion.
 3. A flame spreader as claimed in claim 1 wherein the stress relief portion includes a strip extending transversely in opposing directions from the one strut, said strip having a width less than the width of the one strut and having a length extending from the one strut to the spreader portion greater than the width of the one strut.
 4. A burner apparatus operable at a high rate and a low rate comprising a round burner member disposed about a vErtical axis and having an inlet and a plurality of outward directed ports circumferentially spaced in the burner member to produce an outward extending flame at the high rate and an upward extending flame at the low rate; and a flame spreader having a plurality of struts extending radially from the burner member with openings between the struts for allowing passage of flame, an annular flame spreader portion for spreading the outward extending flame, and a plurality of stress relief portions joining the plurality of struts to the annular flame spreader portion.
 5. A burner apparatus as claimed in claim 4 which includes a flame shield mounted on the annular flame spreader portion and extending around the path of the upward extending flame.
 6. A burner apparatus as claimed in claim 4 wherein each of the plurality of stress relief portions includes a strip extending transversely in opposing directions from a respective strut and having a length extending from the respective strut to the spreader portion greater than the width of the respective strut.
 7. A burner apparatus operable at a high rate and a low rate comprising an annular burner member disposed about a vertical axis and having an inlet and a plurality of outward directed ports circumferentially spaced in the burner member; control means for selectively applying gaseous fuel at a low pressure to the inlet of the burner member to produce an upward extending flame from the ports, and applying gaseous fuel at a high pressure to the inlet of the burner member to produce an outward projecting flame from the ports; a flame spreader having a flame spreading rim, a collar mounted on the burner member above the ports, and a plurality of struts extending radially from the collar to the flame spreading rim; said struts, collar and rim forming openings for passing the upward extending flame; a flame sensing element disposed along the axis of the burner member and extending above the burner member in the path of the upward extending flame; safety valve means responsive to the flame sensing element for controlling fuel flow to the burner member; means responsive to the application of high pressure fuel to the burner member for directing a flame at the flame sensing element; a flame shield mounted on the flame spreading rim of the flame spreader; said rim having flexible elongated partially severed arcuate portions transverse to the struts joining the struts to the rim, and said arcuate portions having widths less than the widths of the struts and having lengths greater than the widths of the struts.
 8. A burner apparatus as claimed in claim 7 which includes water containing means disposed in heat transfer relationship relative to the rim. 